Nanostructured noble metal surfaces enhance the photoluminescence emitted by fluorescent molecules, permitting the development of highly sensitive fluorescence immunoassays. To this end, surfaces with silicon nanowires decorated with silver nanoparticles in the form of dendrites or aggregates were evaluated as substrates for the immunochemical detection of two ovarian cancer indicators, carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4). The substrates were prepared by metal-enhanced chemical etching of silicon wafers to create, in one step, silicon nanowires and silver nanoparticles on top of them. For both analytes, non-competitive immunoassays were developed using pairs of highly specific monoclonal antibodies, one for analyte capture on the substrate and the other for detection. In order to facilitate the identification of the immunocomplexes through a reaction with streptavidin labeled with Rhodamine Red-X, the detection antibodies were biotinylated. An in-house-developed optical set-up was used for photoluminescence signal measurements after assay completion. The detection limits achieved were 2.5 U/mL and 3.12 pM for CA125 and HE4, respectively, with linear dynamic ranges extending up to 500 U/mL for CA125 and up to 500 pM for HE4, covering the concentration ranges of both healthy and ovarian cancer patients. Thus, the proposed method could be implemented for the early diagnosis and/or prognosis and monitoring of ovarian cancer.

The potential distribution in a MEMS capacitor with a thin dielectric film on the bottom electrode and under the presence of field emission leakage current is presented for the first time. The paper also demonstrated the build-up of dielectric charging during this process. The investigation is based on obtaining current-voltage characteristics in clockwise and counter clockwise loops and analyzing the transport mechanisms in MIM capacitors. Same procedure is applied to monitor the dielectric charging build-up during field emission in MEMS capacitors. The data of pristine current-voltage characteristics in both MIM and MEMS are used to determine the Voltage drops across the dielectric film and the gap as well as their dependence on the flowing current.

In this work we demonstrate a two-pixel solid-state photoluminescent device able to emit white light covering the entire visible spectrum from 380nm up to 800nm. The device is based on a combination of porous Si, hydrothermally grown ZnO and carbon quantum dots, in a two-pixel formation, with porous Si and ZnO acting independently while the carbon quantum dots are deposited on top of the entire device. All processing is done using standard Si processing techniques. Moreover, the device design allows for tunability of the emitted spectrum simply by choosing the desired combination of the materials. Overall, the demonstrated device is low cost, environmentally safe and biocompatible.

Noble metal nanostructured substrates enhance photoluminescence emitted from molecules immobilized onto their surface, allowing for the development of highly sensitive immunoassays employing fluorescent labels. In this work, nanostructured silver surfaces were implemented as substrates for the immunochemical detection of two ovarian cancer markers, carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4). Biotinylated detection antibodies were used to allow for the detection of immunocomplexes through a reaction with streptavidin conjugated to Rhodamine Red-X. The detection limits achieved were 2.5 U/mL and 0.06 ng/mL for CA125 and HE4, respectively, with linear dynamic ranges, covering the concentration ranges of both healthy and ovarian cancer patients.

Early diagnosis and monitoring are essential for the effective treatment and survival of patients with different types of malignancy. To this end, the accurate and sensitive determination of substances in human biological fluids related to cancer diagnosis and/or prognosis, i.e., cancer biomarkers, is of ultimate importance. Advancements in the field of immunodetection and nanomaterials have enabled the application of new transduction approaches for the sensitive detection of single or multiple cancer biomarkers in biological fluids. Immunosensors based on surface-enhanced Raman spectroscopy (SERS) are examples where the special properties of nanostructured materials and immunoreagents are combined to develop analytical tools that hold promise for point-of-care applications. In this frame, the subject of this review article is to present the advancements made so far regarding the immunochemical determination of cancer biomarkers by SERS. Thus, after a short introduction about the principles of both immunoassays and SERS, an extended presentation of up-to-date works regarding both single and multi-analyte determination of cancer biomarkers is presented. Finally, future perspectives on the field of SERS immunosensors for cancer markers detection are briefly discussed.

Glutathione and malondialdehyde are two compounds commonly used to evaluate the oxidative stress status of an organism. Although their determination is usually performed in blood serum, saliva is gaining ground as the biological fluid of choice for oxidative stress determination at the point of need. For this purpose, surface-enhanced Raman spectroscopy (SERS), which is a highly sensitive method for the detection of biomolecules, could offer additional advantages regarding the analysis of biological fluids at the point of need. In this work, silicon nanowires decorated with silver nanoparticles made by metal-assisted chemical etching were evaluated as substrates for the SERS determination of glutathione and malondialdehyde in water and saliva. In particular, glutathione was determined by monitoring the reduction in the Raman signal obtained from substrates modified with crystal violet upon incubation with aqueous glutathione solutions. On the other hand, malondialdehyde was detected after a reaction with thiobarbituric acid to produce a derivative with a strong Raman signal. The detection limits achieved after optimization of several assay parameters were 50 and 3.2 nM for aqueous solutions of glutathione and malondialdehyde, respectively. In artificial saliva, however, the detection limits were 2.0 and 0.32 μM for glutathione and malondialdehyde, respectively, which are, nonetheless, adequate for the determination of these two markers in saliva.

In this study, we developed active substrates consisting of Ag-decorated silicon nanowires on a Si substrate using a single-step Metal Assisted Chemical Etching (MACE) process, and evaluated their performance in the identification of low concentrations of Rhodamine 6G using surface-enhanced photoluminescence spectroscopy. Different structures with Ag-aggregates as well as Ag-dendrites were fabricated and studied depending on the etching parameters. Moreover, the addition of Au nanoparticles by simple drop-casting on the MACE-treated surfaces can enhance the photoluminescence significantly, and the structures have shown a Limit of Detection of Rhodamine 6G down to 10−12 M for the case of the Ag-dendrites enriched with Au nanoparticles.

Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and organic solar cells (OSCs). Pristine (referred to as C-dots) and nitrogen-functionalized (referred to as NC-dots) carbon dots are systematically studied regarding their properties by using cyclic voltammetry, Fourier-transform infrared (FTIR) and UV–Vis absorption spectroscopy in order to reveal their energetic alignment and possible interaction with the organic semiconductor’s emissive layer. Atomic force microscopy unravels the ultra-thin nature of the interlayers. They are next applied as interlayers between an Al metal cathode and a conventional green-yellow copolymer—in particular, (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)], F8BT)—used as an emissive layer in fluorescent OLEDs. Electrical measurements indicate that both the C-dot- and NC-dot-based OLED devices present significant improvements in their current and luminescent characteristics, mainly due to a decrease in electron injection barrier. Both C-dots and NC-dots are also used as cathode interfacial layers in OSCs with an inverted architecture. An increase of nearly 10% in power conversion efficiency (PCE) for the devices using the C-dots and NC-dots compared to the reference one is achieved. The application of low-cost solution-processed materials in OLEDs and OSCs may contribute to their wide implementation in large-area applications.